Polyamide-based concentrated solution, use thereof in methods for making polyamide compositions and resulting compositions

ABSTRACT

The invention concerns concentrated solutions based on polyamide used for introducing an additive into a thermoplastic matrix. The concentrated solutions comprise a matrix and an additive, the matrix being a modified polyamide having a star-shaped or H-shaped structure.

The invention relates to concentrated polyamide-based solutions used forintroducing an additive into a thermoplastic matrix. The concentratedsolutions comprise a matrix and an additive, the matrix being a modifiedpolyamide having a star or H structure.

The present invention relates to novel concentrated polyamide-basedsolutions for improving the quality of the compositions obtained usingthese solutions or for improving the performance of the processes forobtaining them.

To manufacture polyamide-based articles, for example moulded articles,films, yarns, fibres or filaments, compositions are mostly used whichcomprise the polyamide and additives. These additives are intended tomodify and improve the behaviour of the polyamide with regard to certainproperties. Mention may be made, for example, of heat or lightstability, coloration, thermomechanical properties, fire retardancy.

These additives may also aid the manufacture of the compositions andarticles obtained therefrom. They may, for example, be catalysts orlubricants.

To produce polymer compositions containing additives, it is commonpractice to use concentrated thermoplastic solutions. These concentratedsolutions are compositions which comprise a thermoplastic matrix and theadditive, preferably in a relatively high concentration, and areintended to be melt-blended with the polymer to which it is desired toadd the additive. The concentrated solution is in general introduced inthe form of granules into an extruder.

This method of incorporation has several advantages. It may allowcompositions very dilute in terms of additive to be obtained with goodcontrol and it may allow several types of composition to be easilyproduced on the same line, without it being necessary to adapt the lineto the form of the additive. All these advantages are known to thoseskilled in the art.

Thus, there are commercially available concentrated thermoplasticsolutions comprising useful additives for producing polymercompositions. These concentrated solutions differ from one another bythe nature of the matrix and the nature and concentration of theadditives. In some cases, the concentrated solutions are prepared asintermediate products for the companies selling final compositions orfinished articles.

To obtain the best possible compositions, it is generally preferred forthe matrix of the concentrated solution used for incorporating theadditives to be of the same nature, or of as similar a nature aspossible, as the polymer on which the final composition is based. Thus,it is known to use matrices made of nylon-6 or nylon-6,6 for theincorporation of additives into compositions based on nylon-6 ornylon-6,6. This practice is widely used in the fields of engineeringplastics and the manufacture of spun articles.

Firstly, the use of concentrated solutions entails additional productioncosts; it involves several melt-blending processes, one for producingthe masterbatch and one for incorporating it into the polymer of thecomposition. The manufacture and the use of highly concentratedsolutions limits the additional cost.

It is a first object of the invention to provide novel polyamide-basedconcentrated solutions with a high concentration of additives.

Secondly, certain additives require special conditions to incorporatethem into the matrix of the concentrated solution and then into thefinal compositions. These are, for example, additives which are unstableto the heat induced by the heating and/or the shear produced duringincorporation. From another standpoint, the heat and/or shear may causethe polymer to undergo degradation. In order to limit these problems, itis known to use special matrices such as EVA. This polymer is not verycompatible with polyamides. It is also known to use nylon-6, -6,6 and-6,10 random copolymers. The cost of these matrices is high. In the caseof the manufacture of compositions based on nylon-6 or nylon-6,6, thesealso result in the incorporation of different repeat units, which mayhave a low degree of compatibility with the polyamide and modify theproperties of the polyamide.

It is a second object of the invention to provide masterbatches makingit possible to obviate these difficulties, by operating at a lowertemperature and/or with less shear, using a matrix based on polyamideunits and to introduce the minimum amount of units not consistent withthe polymer.

The invention therefore provides a concentrated solution comprising apolyamide-based matrix and an additive chosen from fire retardants,pigments, dyes, stabilizers, lubricants, catalysts, processing aids,nucleating agents and mixtures thereof, characterized in that the matrixis a macromolecular compound comprising

-   -   star- or H-configured macromolecular chains comprising a core        and at least three polyamide branches linked to the core,    -   optionally, linear polyamide macromolecular chains,        the weight ratio of the star-configured macromolecular chains to        the sum of the star-configured and linear macromolecular chains        being between 1 and 0.1 and in that the melt flow index of the        matrix measured according to the ISO 1133 standard at 275° C.        under a load of 100 g is greater than 20 g/l 0 min.

The concentrated polyamide solutions according to the invention areindustrial products usually packaged in granule form and intended to beused for the manufacture of polymer compositions containing additives.These compositions are obtained by melt-blending a thermoplastic polymerwith the concentrated solution, for example using an extruder.

The compositions obtained are formed after the melt-blending phase.According to a first process, the composition is formed into granules,which will subsequently be remelted for a final forming operation.According to a second process, the compositions undergo a final formingoperation just after the blending phase, without there being anyintermediate solidification or remelting. As examples of final formingoperations, mention may be made of injection moulding, extrusion andspinning.

The concentrated solutions comprising a thermoplastic matrix and anadditive are generally intended to be used for manufacturing polymercompositions containing additives. In general, the concentratedsolutions are highly concentrated in terms of additives compared withthe polymeric compositions for which they are intended, thesecompositions generally being very dilute in terms of additives. For mostadditives, it may be considered that a concentrated solution comprisesat least 10% by weight of additive.

According to a preferred characteristic of the invention, the proportionby weight of additive in the concentrated solution is greater than orequal to 10%.

The concentrated solution according to the invention comprises anadditive and a matrix, characterized in that the matrix is amacromolecular compound whose characteristics were mentioned above. Theinvention also relates to the use of these macromolecular compounds asthe matrix of a concentrated polyamide solution.

The matrix of the concentrated solution comprises star- or H-configuredmacromolecular chains. Such chains, or polymers comprising such chains,are described, for example in documents FR 2 743 077, FR 2 779 730, U.S.Pat. No. 5,959,069, EP 0 632 703, EP 0 682 057 and EP 0 832 149. Thesecompounds are known for having a better melt flow than linear polymers.The melt flow index of the matrix, measured according to the ISO 1133standard at 275° C. under a load of 100 g is greater than 20 g/10 min.

The star- or H-configured macromolecular chains are obtained by using amultifunctional compound having at least three reactive functionalgroups, all the reactive functional groups being identical. Thiscompound can be used as a comonomer in the presence of other monomers ina polymerization process. It can also be brought into contact with apolyamide during an extrusion step.

The star- or H-configured macromolecular chains comprise a core and atleast three polyamide branches. The branches are linked to the core by acovalent bond via an amide group or a group of another kind. The core isan organic or organometallic chemical compound, preferably a hydrocarboncompound which possibly includes heteroatoms and to which the branchesare linked. The branches are polyamide chains. They may be branched,this being especially the case in H structures. The polyamide chainsconstituting the branches are preferably of the type of those obtainedby the polymerization of lactams or amino acids, for example of thenylon-6 type.

Optionally, the matrix comprises, apart from the star chains, linearpolyamide macromolecular chains. The ratio by weight of the amount ofstar chains in the matrix to the sum of the amounts of star and linearchains is between 1 and 0.1, limits inclusive. It is preferably between0.9 and 0.6.

According to a first process, the matrix may be obtained bycopolymerization starting with a monomer mixture comprising:

-   -   a) a multifunctional compound comprising at least three reactive        functional groups chosen from amines, carboxylic acids and        derivatives thereof, all the reactive functional groups being        identical,    -   b) monomers of the following general formulae (IIa) and (IIb):        X—R₂Y  (IIa)        or    -   c) optionally, monomers of the following general formula (III):        Z—R₃—Z  (III)        in which:    -   Z represents a functional group identical to that of the        reactive functional groups of the multifunctional compound        -   R₂, R₃, which are identical or different, represent            substituted or unsubstituted, aliphatic, cycloaliphatic or            aromatic hydrocarbon radicals containing from 2 to 20 carbon            atoms and possibly including heteroatoms,        -   Y is a primary amine functional group when X represents a            carboxylic acid functional group, or        -   Y is a carboxylic acid functional group when X represents a            primary amine functional group.

The term “carboxylic acid” is understood to mean carboxylic acids andderivatives thereof, such as acid anhydrides, acid chlorides, esters,etc. The term “amine” is understood to mean amines and derivatives.

Such production processes are described in documents FR 2 743 077 and FR2 779 730.

If a comonomer c) is used, the polymerization reaction(polycondensation) is advantageously carried out until thermodynamicequilibrium is achieved.

The monomer mixture may include other compounds, such as chain stoppers,catalysts, or additives.

This process results in the formation of star-configured macromolecularchains and, optionally, linear macromolecular chains. The percentageratio PS of the number of star-configured macromolecular chains to thetotal number of chains is determined by the following formulae:

-   -   if the multifunctional compound has 4 reactive functional        groups:        ${PS} = {\frac{{4\quad T_{0}{X_{d}^{3}\left( {1 - X_{d}} \right)}} + {T_{0}X_{d}^{4}}}{\begin{matrix}        {{N_{0}\left( {1 - X_{d}} \right)} - {2R_{0}X_{d}} - {4\quad T_{0}X_{d}} +} \\        {{R_{0}\left\lbrack {1 - \left( {1 - X_{d}} \right)^{2}} \right\rbrack} + {T_{0}\left\lbrack {1 - \left( {1 - X_{d}} \right)^{4}} \right\rbrack}}        \end{matrix}} \times 100}$ in  which:        $X_{d} = {1 - \frac{\lbrack{COOH}\rbrack}{{2\quad R_{0}} + {4\quad T_{0}} + N_{0}}}$        if the reactive functional groups are acid functional groups;        $X_{d} = {1 - \frac{N_{0} - \lbrack{NH2}\rbrack}{{2\quad R_{0}} + {4\quad T_{0}} + N_{0}}}$        if the reactive functional groups are amine functional groups;

-   T₀ represents the number of moles of multifunctional compound;

-   N₀ represents the initial number of moles of monomer of formula    (IIa) or (IIb);

-   R₀ represents the initial number of moles of 5monomer of formula    (III);    -   if the multifunctional compound has 3 reactive functional        groups:        ${PS} = {\frac{T_{0}X_{d}^{3}}{{N_{0}\left( {1 - X_{d}} \right)} - {R_{0}X_{d}} - {3\quad T_{0}X_{d}} + {T_{0}\left\lbrack {1 - \left( {1 - X_{d}} \right)^{3}} \right\rbrack}} \times 100}$        in which:        if the reactive functional groups are acid functional groups;        $X_{d} = {1 - \frac{\lbrack{COOH}\rbrack}{{2\quad R_{0}} + {3T_{0}} + N_{0}}}$        if the reactive functional groups are amine functional groups;        $X_{d} = {1 - \frac{N_{0} - \lbrack{NH2}\rbrack}{{2\quad R_{0}} + {3\quad T_{0}} + N_{0}}}$

-   T₀ represents the number of moles of multifunctional compound;

-   N₀ represents the initial number of moles of monomer of formula    (IIa) or (IIb);

-   R₀ represents the initial number of moles of monomer of formula    (III).

According to a second process, the matrix comprises H-configuredmacromolecular chains, the matrix being obtained by copolymerizationstarting from a monomer mixture comprising:

-   -   a) 1 to 50 μmol per gram of matrix of a multifunctional compound        comprising at least three reactive functional groups chosen from        amines, carboxylic acids and derivatives thereof, the reactive        functional groups being identical;    -   b) lactams and/or amino acids;    -   c) a multifunctional compound c) chosen from dicarboxylic acids        or diamines;    -   d) a monofunctional compound, the functional group of which is        chosen from amines, carboxylic acids and derivatives thereof,        the functional groups of c) and d) being amines when the        functional groups of a) are acids, the functional groups of c)        and d) being acids when the functional groups of a) are amines,        the ratio in terms of equivalents of the functional groups of a)        to the sum of the functional groups of c) and d) being between        1.5 and 0.66 and the ratio in terms of equivalents of the        functional groups of c) to the functional groups of d) being        between 0.17 and 1.5.

Such a process and such polymers are described in the document U.S. Pat.No. 5,959,069.

According to a third process, the matrix may be obtained by themelt-blending, for example using an extruder, of a polyamide of the typeof those obtained by the polymerization of lactams and/or of aminoacids, and of a multifunctional compound comprising a core and at leastthree branches, all the branches of which have identical terminalfunctional groups chosen from amines, carboxylic acids and derivativesthereof. The polyamide is, for example, nylon-6.

Such production processes are described in documents EP 0 682 070 and EP0 672 703.

The multifunctional compounds used may be chosen from compounds having adendritic or tree structure. They may also be chosen from compoundsrepresented by the formula (I):R1A—z]_(m)  (I)in which:

-   -   R₁ is an aromatic or aliphatic, linear or cyclic, hydrocarbon        radical containing at least two carbon atoms and possibly        including heteroatoms;    -   A is a covalent bond or an aliphatic hydrocarbon radical        containing from 1 to 6 carbon atoms;    -   Z represents a primary amine functional group or a carboxylic        acid functional group; and    -   m is an integer between 3 and 8.

According to a preferred characteristic, the radical R₁ is either acycloaliphatic radical, such as the tetravalent cyclohexanonyl radical,or a propane-1,1,1-triyl or propane-1,2,3-triyl radical.

As other radicals R₁ suitable for the invention, mention may be made, byway of example, of substituted or unsubstituted trivalent phenyl andcyclohexanyl radicals, tetravalent diaminopolymethylene radicals with anumber of methylene groups advantageously between 2 and 12, such as theradical originating from EDTA (ethylenediaminetetraacetic acid),octovalent cyclohexanonyl or cyclohexanedionyl radicals, and radicalsoriginating from compounds resulting from the reaction of polyols, suchas glycol, pentaerythritol, sorbitol or mannitol, with acrylonitrile.

The radical A is preferably a methylene or polymethylene radical, suchas the ethylene, propylene or butylene radicals, or a polyoxyalkyleneradical, such as the polyoxyethylene radical.

According to a preferred embodiment of the invention, the number m isgreater than 3 and advantageously equal to 3 or 4.

The reactive functional group of the multifunctional compoundrepresented by the X—H symbol is a functional group capable of formingan amide functional group.

Mention may be made, as examples of polyfunctional compounds of formula1, of the compound 2,2,6,6-tetra(β-carboxyethyl)cyclohexanone, thecompound diaminopropane-N,N,N′,N′-tetraacetic acid of the followingformula:

or compounds originating from the reaction of trimethylolpropane or ofglycerol with propylene oxide and amination of the end hydroxyl groups;the latter compounds are sold under the trade name JEFFAMINES T® byHuntsman and have the general formula:

in which:

-   -   R₁ represents a propane-1,1,1-triyl or propane-1,2,3-triyl        radical,    -   A represents a polyoxyethylene radical.

Examples of suitable multifunctional compounds are, for example, citedin document U.S. Pat. No. 5,346,984, in document U.S. Pat. No.5,959,069, in document WO 96/35739 and in document EP 672 703.

The following may more particularly be mentioned:

-   -   nitrilotrialkylamines, in particular nitrilotriethylamine,        dialkylene-triamines, in particular diethylenetriamine,        trialkylenetetramines and tetraalkylene-pentamines, the alkylene        preferably being ethylene and 4-aminoethyl-1,8-octanediamine.

Mention may also be made of the dendrimers of formula (II):(R₂ N—(CH₂)_(n))₂—N—(CH₂)_(x)—N—((CH₂)_(n)—NR₂)₂  (II)in which

-   -   R is a hydrogen atom or a —(CH₂)_(n)—NR¹ ₂ group, in which    -   R¹ is a hydrogen atom or a —(CH₂)_(n)—NR² ₂ group, in which    -   R² is a hydrogen atom or a —(CH₂)_(n)—NR³ ₂ group, in which    -   R³ is a hydrogen atom or a —(CH₂)_(n)—NH₂ group,    -   n being an integer between 2 and 6 and    -   x being an integer between 2 and 14.        n is preferably an integer between 3 and 4, in particular 3, and        x is preferably an integer between 2 and 6, preferably between 2        and 4, in particular 2.        Each radical R may be chosen independently of the others. The        radical R is preferably a hydrogen atom or a —(CH₂)_(n)—NH₂        group.        Mention may also be made of multifunctional compounds having 3        to 10, preferably 3 or 4, carboxylic acid groups. Among these,        compounds having an aromatic and/or heterocyclic ring are        preferred, for example benzyl, naphthyl, anthracenyl, biphenyl        and triphenyl radicals, or heterocycles, such as pyridine,        bipyridine, pyrrole, indole, furan, thiophene, purine,        quinoline, phenanthrene, porphyrine, phthalocyanine and        naphthalocyanine. Most particularly preferred are        3,5,3′,5′-biphenyltetracarboxylic acid, acids derived from        phthalocyanine and from naphthalocyanine,        3,5,3′,5′-biphenyltetracarboxylic acid,        1,3,5,7-naphthalenetetracarboxylic acid,        2,4,6-pyridinetricarboxylic acid, 3,5,        3′,5′-bipyridyltetracarboxylic acid, 3,5,        3′,5′-benzophenonetetracarboxylic acid,        1,3,6,8-acridinetetracarboxylic acid, and more particularly        still trimesic acid and 1,2,4,5-benzenetetracarboxylic acid.        Mention may also be made of multifunctional compounds whose core        is a heterocycle having a point of symmetry, such as        1,3,5-triazines, 1,4-diazines, melamine, compounds derived from        2,3,5,6-tetraethylpiperazine, 1,4-piperazines and        tetrathiafulvalenes.        Mention may more particularly be made of        1,3,5-triazine-2,4,6-tri(aminocaproic acid) (TTACA).

The additives are chosen from fire retardants, pigments or dyes,minerals or organometallics, polyamide polycondensation catalysts,processing aids, such as waxes, and light and UV stabilizers for thepolymers.

As examples of fire retardants, mention may be made of phosphoruscompounds, such as red phosphorus and coated or passivated redphosphorus; halogenated compounds, such as PDBS and brominatedpolystyrenes; melamine-based compounds, such as melamine cyanurate,compounds based on magnesium hydroxide or oxide, zinc derivatives, suchas zinc borate, zinc oxide or zinc stannate, and antimony dioxide.

The additive may be chosen from organic or organometallic dyes andpigments or mineral dyes. As examples of pigments, mention may be madeof titanium dioxide particles, these optionally being coated, and carbonblacks, phthalocyanine-based pigments and azo pigments.

According to one feature of the invention, the proportion by weight ofadditive in the concentrated polyamide solution is greater than 10%.

According to a particular embodiment, the additive consists of particlesbased on titanium oxide, in a weight concentration of greater than 65%.

The concentrated solutions according to the invention are prepared bythe melt-incorporation of the additive into the matrix. This operationis advantageously carried out using an extruder, in which the materialis melted, transported and possibly sheared. The amount of powersupplied to the extruder is advantageously less than that needed tocarry out the same operation with a matrix based on a linear polyamide.The extrusion conditions are advantageously chosen so that thetemperature in the extruder is not too high. Under these conditions, theadditive is well dispersed in the matrix, even with a highconcentration.

According to one particular embodiment of the invention, theconcentrated solution is obtained by introducing, into an extruder, theadditive, a multifunctional compound as defined above and a polyamide,during the same extrusion step. The process consists in simultaneouslyobtaining the star-configured macromolecular chains and introducing theadditive into the matrix.

The invention also relates to a process for manufacturing polymercompositions and to polymer compositions comprising the concentratedpolyamide solution.

The polymer compositions are obtained by melt-blending a thermoplasticpolymer with the concentrated solution, for example using an extruder.

The thermoplastic polymer is preferably chosen from polyamides, morepreferably from polymers based on nylon-6 or on nylon-6,6. According toa preferred embodiment of the invention, 99% by weight of the repeatunits of the macromolecular chains within the composition are chosenfrom nylon-6 repeat units and nylon-6,6 repeat units.

The compositions are advantageously obtained by melt-blending thethermoplastic polymer with the concentrated polyamide solution using anextruder. The amount of power supplied to the extruder in order to melt,transport and possibly shear the material is low. The temperatureprofile within the extruder is advantageously adjusted so as to preventthe thermoplastic polymer from degrading.

Further details or advantages of the invention will become more clearlyapparent in the light of the examples given below solely by way ofindication.

EXAMPLES 1 TO 10

Concentrated polyamide solutions based on several additives and onseveral types of matrix were produced:

-   -   Matrix 1: a nylon-6 of 37 relative viscosity measured in formic        acid;    -   Matrix 2: a nylon-6 of 2.7 relative viscosity measured in        sulphuric acid;    -   Matrix 3: a star nylon-6 obtained by polymerizing caprolactam in        the presence of 2,2,6,6-tetra-(β-carboxyethyl)cyclohexanone,        using a process described in document FR 2 743 077, having a        melt flow index of 55 g/10 min at 275° C./100 g;    -   Additive 1: zinc borate sold by Borax under the name FIREBRAKE        ZB;    -   Additive 2: titanium dioxide particles sold by Kronos Europe        under the name KRONOS Cl 220;    -   Additive 3: organic black pigment sold by Bayer under the name        NIGROSINE BASE BA;    -   Additive 4: inorganic black pigment sold by Degussa under the        name PRINTEX 85; and    -   Additive 5: melamine cyanurate sold by DSM Melapur under the        name MELAPUR MC 25.

The additive was incorporated into the matrix using a twin-screwextruder of the Werner and Pfleiderer ZSK40 type with a throughput of 30kg/h. The concentrated solution was extruded in the form of rods.

The amount of power supplied to the system was evaluated based on theelectrical current (in amps).

For each matrix/additive combination, the maximum amount of additivethat it was possible to incorporate was determined. This is defined asthe amount of additive above which the rod breaks.

The results are given in Table I. TABLE I 6 7 (compar- 8 (compar- 9(compar- 10 (compar- Example 1 2 3 4 5 (compara-tive) ative) ative)ative) ative) Matrix 3 3  3  3  3 1 1  2  2  2 Additive 1 2  3  4  5 1 2 3  4  5 Extrusion 240 240 230-240 230-240 230-240 240 240 245-255250-260 245-255 temperature (° C.) Maximum 75 85 60 40 60 65 80 40 25 40amount of additive (%) Current (A) 28 14 35 38 29 38 36 39 42 35

FIG. 1 shows a photograph of a rod observed in an SEM microscopecomprising 80% titanium dioxide in matrix 3. FIG. 2 shows a photographof a rod observed in an SEM microscope, comprising 80% titanium dioxidein matrix 1. It may be seen that the rod shown in FIG. 1 has, accordingto the invention, a smooth and crater-free surface.

EXAMPLE 11

Using an extruder of the same type as that used for Examples 1 to 10, 5%of the concentrated solution of Example 2 was introduced into a nylon-6.

The additive in the composition obtained was extremely well dispersed.FIG. 3 is a photograph of a cross section through a rod obtained. FIG. 4is a photograph of a rod obtained in a similar manner from aconcentrated polyamide solution according to Example 7. Much betterdispersion of the additive is observed when using the concentratedsolution of Example 2.

EXAMPLE 12

Using an extruder of the same type as that used for Examples 1 to 10, 5%of the concentrated polyamide solution of Example 1 was introduced intoa nylon-6.

The compositions showed excellent dispersion of the additive.

EXAMPLES 13 AND 14

Concentrated polyamide solutions were produced from ared-phosphorus-based fire retardant sold by Italmatch and from severaltypes of matrix described above.

The additive was incorporated into the matrix using a twin-screwextruder of the Werner and Pfleiderer ZSK70 type, with a throughput of260 kg/h and a screw rotation speed of 150 rpm. The concentratedsolution was extruded in the form of rods.

For each matrix/additive combination, the maximum amount of additivethat it was possible to incorporate was determined. This is defined asthe amount of additive above which the rod breaks.

The results are given in Table II. TABLE II Example 13 14 (comparative)Matrix  3  2 Extrusion temperature (° C.) 230-250 245-275 Amount ofadditive (%) 72-75 50-53 Die pressure (bar) 17-19 25-28 Maximum amountof 80 60 additive (%)

EXAMPLES 15 AND 16

Concentrated polyamide solutions were produced from several waxes andfrom several types of matrix, described above.

The additive was incorporated into the matrix using a twin-screwextruder of the Werner and Pfleiderer ZSK40 type, with a throughput of30 kg/h.

The concentrated solution was extruded in the form of rods.

Extrusion temperature: 250° C.

For each matrix/additive combination, the maximum amount of additivethat it was possible to incorporate was determined. This is defined asthe amount of additive above which the rod breaks.

The results are given in Table Ill. TABLE III Example 15 16(comparative) Matrix 3 2 Amount of matrix (%) 94 94 Amount of EBS(ethylene 3 3 bis(stearamide)) (%) Amount of calcium stearate (%) 2 2Amount of aluminium stearate (%) 1 1 Total amount of wax (%) 6 6 Totalmaximum amount of wax (%) 12 6

EXAMPLES 17 AND 18

Using an extruder of the same type as that used for Examples 15 and 16,10% of the concentrated solution of Example 15 was introduced into anylon-6,6 of 2.7 relative viscosity measured in sulphuric acid.

Likewise, 10% of the concentrated solution of Example 16 was introducedinto a nylon-6,6 of 2.7 relative viscosity measured in sulphuric acid.

The composition obtained was formed into a collar by moulding using thefollowing operating conditions:

-   -   mould temperature (water): 80° C.;    -   barrel temperature: 320° C.;    -   hold time: 2 s;    -   injection rate: 550 cm³/s;    -   screw speed: 200 rpm;    -   back-pressure: 5 bar.

The results are given in Table IV TABLE IV Example 17 18(comparative)Identical to Identical to Concentrated solution Example 15 Example 16Injection pressure (bar) 111 150 Hold pressure  75  75 (bar) Cycletime(s)  9  9

The composition of Example 17 was easier to mould than the compositionof Example 18. Composition 17 also had good mechanical properties,especially a good cold impact strength.

1. Concentrated solution comprising a polyamide-based matrix and anadditive selected from the group consisting of fire retardants,pigments, dyes, stabilizers, lubricants, catalysts, processing aids,nucleating agents and mixtures thereof, wherein the matrix is amacromolecular compound comprising star- or H-configured macromolecularchains comprising a core and at least three polyamide branches linked tothe core, optionally, linear polyamide macromolecular chains, the weightratio of the star-configured macromolecular chains to the sum of thestar-configured and linear macromolecular chains being between 1 and 0.1and in that the melt flow index of the matrix measured according to theISO 1133 standard at 275° C. under a load of 100 g is greater than 20g/10 mm.
 2. Concentrated solution according to claim 1, which includesat least 10% by weight of additive.
 3. Concentrated polyamide solutionaccording to claim 1, wherein the matrix is obtained by copolymerizationstarting with a monomer mixture comprising: a) a multifunctionalcompound comprising at least three reactive functional groups chosenfrom amines, carboxylic acids and derivatives thereof, the reactivefunctional groups being identical, b) monomers of the following generalformulae (IIa) and (IIb):X—R₂—Y  (IIa)or

c) optionally, monomers of the following general formula (III):Z-R₃-Z  (III) in which: Z represents a functional group identical tothat of the reactive functional groups of the multifunctional compoundR₂, R₃, which are identical or different, represent substituted orunsubstituted, aliphatic, cycloaliphatic or aromatic hydrocarbonradicals containing from 2 to 20 carbon atoms and optionally includingheteroatoms, Y is a primary amine functional group when X represents acarboxylic acid functional group, or Y is a carboxylic acid functionalgroup when X represents a primary amine functional group. 4.Concentrated solution according to claim 1, wherein the matrix isobtained by copolymerization starting from a monomer mixture comprising:a) 1 to 50 μmol per gram of matrix of a multifunctional compoundcomprising at least three reactive functional groups selected from thegroup consisting of amines, carboxylic acids and derivatives thereof,the reactive functional groups being identical; b) lactams and/or aminoacids; c) a multifunctional compound c) comprising dicarboxylic acids ordiamines; d) a monofunctional compound, the functional group of which isselected from the group consisting of amines, carboxylic acids andderivatives thereof, the functional groups of c) and d) being amineswhen the functional groups of a) are acids, the functional groups of c)and d) being acids when the functional groups of a) are amines, theratio in terms of equivalents of the functional groups of a) to the sumof the functional groups of c) and d) being between 1.5 and 0.66 and theratio in terms of equivalents of the functional groups of c) to thefunctional groups of d) being between 0.17 and 1.5.
 5. Concentratedsolution according to claim 1, wherein the matrix is obtained byextruding a polyamide of the type of those obtained by thepolymerization of lactams and/or amino acids with a multi-functionalcompound having at least three reactive functional groups selected fromthe group consisting of amines, carboxylic acids and derivativesthereof, the reactive functional groups being identical.
 6. Concentratedsolution according to claim 3, wherein the multifunctional compound orthe multifunctional monomer has a dendritic or tree structure. 7.Concentrated solution according to claim 3, wherein the multifunctionalcompound is represented by the formula (I):R1A—z]_(m)  (I) in which: R₁ is an aromatic or aliphatic, linear orcyclic, hydrocarbon radical containing at least two carbon atoms andoptionally including heteroatoms; A is a covalent bond or an aliphatichydrocarbon radical containing from 1 to 6 carbon atoms; Z represents aprimary amine radical or a carboxylic group; and m is an integer between3 and
 8. 8. Concentrated solution according to claim 3, wherein themultifunctional compound is selected from the group consisting of2,2,6,6-tetra-(β-carboxyethyl)cyclohexanone, trimesic acid,1,3,5-triazine-2,4,6-tri(aminocaproic acid) and4-aminoethyl-1,8-octanediamine.
 9. Concentrated solution according toclaim 1, wherein the additive is a fire retardant selected from thegroup consisting of melamine-based compounds, halogenated compounds,compounds based on magnesium oxide or hydroxide, compounds based on redphosphorus and zinc-based compounds.
 10. Concentrated solution accordingto claim 1, wherein the additive is a pigment or a mineral dye. 11.Concentrated solution according to claim 10, wherein the additive is anorganic or organometallic dye.
 12. Concentrated solution according toclaim 1, wherein the additive is selected from the group consisting ofheat stabilizers and light or UV stabilizers for polyamides.
 13. Processfor manufacturing a concentrated polyamide solution according to claim1, comprising introducing the matrix and the additive into an extruderand in extruding the melted blend.
 14. Process for manufacturing athermoplastic polymer composition by melt-blending a concentratedsolution with a thermoplastic polymer, wherein the concentrated solutionis a concentrated solution according to claim
 1. 15. Process accordingto claim 14, wherein the thermoplastic polymer is polyamide-based. 16.Polymer composition comprising a thermoplastic polymer and at least oneadditive, which is obtained by melt-blending a thermoplastic polymerwith a concentrated polyamide solution according to claim
 1. 17. Polymercomposition according to claim 16, wherein the macromolecular unitspresent in the composition are selected from the group consisting ofnylon-6 repeat units and nylon-6,6 repeat units.